Data deduplication (often called “intelligent compression” or “single-instance storage”) is a method of reducing storage needs by eliminating redundant data. Data deduplication is often used for backup purposes and for virtual machine image storage. lessfs can determine if data is redundant by calculating an unique (192 bit) tiger hash of each block of data that is written. When lessfs has determined that a block of data needs to be stored it first compresses the block with LZO or QUICKLZ compression.

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